The use of a unitized cartridge mechanical face seal assembly for a rotating shaft sealing system is now well known in the industry. American Petroleum Institute Standard 682 defines a cartridge seal as a “complete self contained unit (including seal faces, flexible elements, seal gland plate, sleeve and mating ring) which is pre-assembled and preset before installation”. The cartridge assembly eliminates the handling of many precision machined parts, measuring, and aligning the seal assembly to a rotating shaft inside the seal assembly housing. The difficulty of coordination and performance of these steps had been one of the leading causes for premature seal failure.
All cartridge seal designs have a sleeve that affixes to the rotating shaft. This sleeve, concentric to the rotating shaft, holds the rotary seal assembly in the correct operating position, and transmits torque to the rotary face.
Cup point set screws are routinely used to secure the rotary face assembly to the sleeve. Because of the inherent design, the use of set screws to secure the rotary face leads to a number of problems including leakage, sleeve distortion, vibration damage, and complete seal failure.